The present invention relates to an image processing method and a device used therefor for generating three-dimensional images to be drawn on a two-dimensional screen, such as on a television monitor, a computer-readable recording medium having recorded thereon an image processing program, a program execution device and an image processing program.
There are accelerating trends in higher integration and faster processing speeds of processors and memories in recent television game machines and personal computers which enable real-time generation of three-dimensional images with real presence and perspective in the display thereof on two-dimensional monitor screens.
When a three-dimensional image is drawn on a two-dimensional monitor screen, the three-dimensional polygon data are subjected to various geometric processing, such as coordinate conversion, clipping and lighting, and the resultant data are further subjected to transparent projection conversion.
In the drawing of a three-dimensional image, the positions of the polygons, which have been given by floating-point representation or fixed-point representation, are converted into integers so as to correspond to pixels at fixed positions on a two-dimensional screen, so that so-called aliasing occurs, which undesirably emphasizes the step-like unsmoothness (so-called jaggedness) of the pixel profile on the edge of the image.
A conventional solution for generating a jagged-free image is to perform so-called anti-aliasing, which is a process for removing or preventing aliasing.
More specifically, the conventional image processing reduces jaggedness by a method of, for example, drawing half-tone data generated by interpolating pixel data, or by virtually dividing one pixel into finer units called sub-pixels, performing calculations such as ray tracing on a sub-pixel basis, and then averaging the calculated results on a pixel basis. In another conventional method of image processing, jaggedness is reduced by anti-aliasing in which a high-resolution image is generated and then filtered to thereby reduce the number of pixels.
Jaggedness due to aliasing tends to be most distinctive at a portion having a particularly high luminance of the image edge. For a case in which the three-dimensional image is a moving image, jaggedness generated at such edge portion having a high luminance will intensify flicker in a displayed image to thereby make such image quite unrecognizable.
However, as the conventional technique reduces jaggedness by processing not only the image edge but also the overall image, an expensive processor device capable of rapid operational processing and a large-capacity, high-speed storage element are required, which inevitably results in a higher price and larger size of the image processing device.